For converting the voltage of a DC power supply to a single-phase AC voltage, for example, a power conversion device including a boost converter (DC/DC converter) and an inverter circuit is used. In a traditional power conversion device, the voltage of a DC power supply is stepped up by a boost converter to a certain voltage higher than the peak voltage on the AC side, and thereafter, the resultant voltage is converted to an AC voltage by an inverter circuit. In this case, the boost converter and the inverter circuit always perform high-speed switching operations. Therefore, switching loss occurs in each switching element and iron loss occurs in a reactor. These losses become a factor for hampering improvement in conversion efficiency.
Meanwhile, the following control is proposed: while the voltage of the DC power supply and the absolute value of the instantaneous voltage on the AC side are always compared with each other, the boost converter is caused to perform switching operation only during a period in which step-up operation is needed, and the inverter circuit is caused to perform switching operation only during a period in which a step-down operation is needed (see, for example, Patent Literature 1, 2). In such control, the period in which the switching operation is stopped is provided to the boost converter and the inverter circuit. If the stop period is provided, switching loss and reactor iron loss are reduced accordingly, leading to improvement in conversion efficiency.